Conformable wound dressing

ABSTRACT

A wound dressing comprising an absorbent pad, an adhesive layer, and a backing layer is described, along with a dressing support layer configured to retain and deliver the wound dressing to a wound, the dressing support layer having a radial configuration that forms a plurality of alternating covered and uncovered portions of the backing layer along the perimeter of the wound dressing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/361,874, filed Feb. 24, 2006 now U.S. Pat. No. 7,518,031, publicationNo. 2006-0142687-A1, which is a continuation of U.S. patent applicationSer. No. 11/026,177, filed Dec. 30, 2004, issued as U.S. Pat. No.7,030,288, which is a continuation of U.S. patent application Ser. No.10/370,249, filed Feb. 19, 2003, now U.S. Pat. No. 6,838,589.

FIELD OF THE INVENTION

The invention relates to wound dressings, and more particularly to athin film composite dressing and a radial support delivery system.

BACKGROUND OF THE INVENTION

Wound dressings using an absorbent central area surrounded by a largeradhesive film are known. For example, U.S. Pat. No. 5,738,642 (the '642patent) shows a wound dressing and delivery system comprising a thickabsorbent pad placed in the center of a thin backing. A carrier framesurrounds the perimeter of the wound dressing, providing sufficientsupport (e.g. rigidity) to the backing to facilitate handling of thedressing during application to a wound. The dressing taught in the '642patent is useful for application to a large variety of wounds. However,a need remains for a wound dressing that can be more effectively appliedto irregular surfaces, such as a heel or shoulder. Currently, wounddressings are sometimes cut toward their center to make a cone shapeddressing, but these dressings have significant limitations, includingthe risk of infection along the line of the cut line, difficulty inapplying with one hand, and leakage of fluids from the wound along thecut line.

Therefore, a need remains for an improved wound dressing configured forapplication to a rounded or other irregularly shaped body part.

SUMMARY OF THE INVENTION

The present invention provides a wound dressing having a thin, flexibleperiphery and delivery system that facilitates handling the wounddressing. The wound dressing is constructed so as to have improvedadhesion to irregular shaped surfaces, such as a heel, and to permiteasy application to the irregular shaped surfaces. The wound dressingand delivery system are well suited to positioning an absorbent pad ontoa concave or convex surface. For example, the wound dressing anddelivery system are suitable for applying an absorbent pad to the heelof a foot, while maintaining an intact sterile perimeter around thewound dressing.

In certain implementations the wound dressing and delivery systeminclude a wound dressing comprising an adhesive layer on a backinglayer. Optionally, an absorbent pad or material is applied or attachedto the adhesive layer. A dressing support layer is positioned on top ofthe backing layer, and is configured to retain and deliver the wounddressing to a wound. In particular, the dressing support layer has aradial configuration of extensions that support the backing layer alongthe perimeter of the wound dressing, while also allowing the dressing tobe easily applied to convex surfaces and other non-planer surfaces.

These and various other advantages and features characterizing theinvention are pointed out with particularity in the claims annexedhereto and forming a part hereof. However, for a better understanding ofthe invention, its advantages, and objects obtained by its use,reference should be made to the accompanying drawings and descriptivematter, in which embodiments of the invention are illustrated anddescribed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be further described with reference to the drawings,wherein corresponding reference characters indicate corresponding partsthroughout the several views, and wherein:

FIG. 1 is a top perspective view of a wound dressing configured andarranged in accordance with an implementation of the invention.

FIG. 2 is a top plan view of the wound dressing of FIG. 1.

FIG. 3 is a side schematic view of the dressing of FIGS. 1 and 2 takensubstantially along line 3-3 of FIG. 2.

FIG. 4 is an enlarged side cross-sectional view of the dressing of FIG.3, the cross section taken along the line 4-4 of FIG. 5.

FIG. 5 is a top plan view of an alternative embodiment of a wounddressing made in accordance with the invention.

FIG. 6 is a top plan view of another alternative embodiment of a wounddressing made in accordance with the invention.

FIG. 7 is a top plan view of yet another alternative embodiment of awound dressing made in accordance with the invention.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

The present invention is directed to a wound dressing and deliverysystem, as well as to methods of applying the wound dressing anddelivery system to a patient. The wound dressing and delivery system areparticularly well suited to application over a convex surface of apatient, such as a patient's heel. The wound dressing permits a highlyabsorbent material to be placed against the wound, while the deliverysystem aids in forming a seal around the convex or irregularly shapedarea surrounding the wound.

In some implementations the wound dressing comprises an absorbent pad, abacking layer, and an adhesive layer on the backing layer facing theabsorbent pad. The adhesive layer and backing layer form a perimeteraround the absorbent pad and hold the absorbent pad in place on a wound.The perimeter formed by the adhesive layer and backing layer keeps theabsorbent pad properly positioned, and also helps maintain a sterileenvironment around the wound. The adhesive layer and backing layer aretypically extremely thin, and generally very flexible. If the adhesivelayer and backing layer are not properly supported during applicationthey can easily fold over and adhere to themselves, preventing properapplication over a wound. The delivery system of the invention providesan easy and effective way to apply the wound dressing to a patient whileeffectively supporting the perimeter of the dressing to preventexcessive undesirable folding, while allowing controlled, limitedfolding of the backing layer sufficient to properly contact thepatient's uneven skin surface.

FIGS. 1 and 2 show an example of a wound dressing and delivery systemmade in accordance with the invention. The wound dressing 10 includes acentrally located absorbent pad 12. The absorbent pad 12 is covered byan adhesive layer 17 on a backing layer 14 that extends out to theperimeter 15 of the wound dressing 10. The backing layer 14 is typicallyextremely thin, flexible, and either transparent or translucent,allowing the absorbent pad 12 to be viewed through it. The deliverysystem of this invention is particularly useful in connection with awound dressing 10 having a relatively heavy or stiff absorbent pad 12positioned on a highly conformable backing layer 14 that is light andflexible relative to the pad 12.

At least one dressing support layer 16 is positioned over the wounddressing 10. In certain implementations of the invention the dressingsupport layer 16 has a substantially radial configuration, with aplurality of extensions 18 radiating generally from the center 19 of thedressing 10. The support layer 16 forms a plurality of alternatinguncovered portions 20 of the adhesive backing layer 14, separated fromone another by the extensions 18 along the adhesive perimeter 15 of thewound dressing. The support layer 16 can be a single piece of material,such as a polymeric film, or can be two or more distinct pieces. Thesupport layer 16 shown in FIGS. 1 and 2 is two separate pieces dividedby joint 28.

In most implementations the support layer 16 comprises a plurality ofextensions 18 radiating from the interior of the dressing 10 toward itsedges. The radial configuration of the dressing support layer 16 allowsthe perimeter 15 of the dressing 10 to be pressed around a convexsurface. During application, the uncovered portions 20 of the backinglayer 14 between the extensions 18 can contract to maintain a good sealaround the edges of the wound. This contraction is typically localizedso that individual portions 20 will contract and even fold uponthemselves. However, folds or contact between the portions 20 isminimized. In this manner, the wound dressing 10 can have a relativelyeven, smooth edge without major flaps of the backing layer 14 foldedover onto itself.

In some implementations, such as those shown in FIGS. 1 and 2, at leastsome of the plurality of extensions 18 narrow as they approach theperimeter 15 of the dressing 10. Also, in some implementations thedressing support layer 16 comprises at least one portion that extendsbeyond the edge of the backing layer 14 of the wound dressing 10 to forma tab 22. The tab 22 can be held during positioning of the wounddressing 10.

In addition, the wound dressing 10 typically includes a carrier film 24,also having a tab 26. The carrier film 24 covers the surface of thewound dressing applied to the patient, generally making contact with theabsorbent pad 12 and the periphery of the adhesive layer 17. The carrierfilm 24 remains attached to wound dressing 10 until a user is ready toapply the dressing. The carrier film 24 may be a single piece ormultiple piece release liner, and may be part of or laminated to thepackage (not shown) containing the dressing, or merely enclosed alongwith the dressing within the package. The carrier film 24 keeps theadhesive clean during storage and shipping of the wound dressing 10.

In the implementation shown in FIGS. 1 and 2, the extensions 18 convergeon the center 19 of the wound dressing 10 but do not cover the center19. In general, the perimeter of the dressing support layer 16 isreleasably adhered to the backing layer 14, but at least part of thecenter portion 19 of the dressing support layer 16 is not adhered to thebacking layer 14. This results in the formation of a plurality ofcentrally located tabs 23 configured for removing the dressing supportlayer from the backing layer after the dressing 10 has been applied to apatient. In some embodiments, at least part of the center of thedressing support layer 16 is prevented from adhering to the backinglayer 14 by means of a liner 23 a on the side of dressing support layer16 facing backing layer 14. This liner 23 a also aids in removal of thesupport layer, and in some embodiments assists in elevating the tabs 23when the dressing 10 is applied to a wound.

In reference now to FIGS. 3 and 4, a side elevational view of the wounddressing 10 from FIGS. 1 and 2 is depicted in FIG. 3, while FIG. 4 is across section of a wound dressing 10 made in accordance with theinvention, taken along lines 4-4 of FIG. 3. This cross section shows anabsorbent pad 12 that is covered by a thin, flexible backing layer 14,which in turn is partially covered by support layer 16 and adhesivelayer 17. FIG. 3 shows important aspects of one implementation of theinvention. However, various other implementations are appropriate inorder to add or take away from the aspects shown in FIG. 4. For example,the backing layer 14 can be multiple films or coatings without divergingfrom the invention or deviating from the meaning of the term “film” asused herein. Similarly, the absorbent pad 12 can include multiplesub-layers, including films, webs, sheets, etc. Also, additional layersand films of other materials can be added between the materialsdescribed herein without deviating from the invention.

The number of exposed areas 20 of backing layer 14 along the perimeter15 of the wound dressing 10 can vary in number, shape, and size.However, typically there are at least six distinct exposed areas,generally at least eight, and more commonly twelve or more distinctareas. In some implementations less than 80 percent of the periphery(that portion outside of the absorbent) of the backing layer 14 iscovered by the support layer 16, while in other implementations lessthan 60 percent of the periphery of the backing layer 14 is covered bythe support layer 16, while in yet other implementations less than 40percent of the periphery of the backing layer 14 is covered by thesupport layer 16.

In some embodiments, separation of the extensions 18 is provided byprecut paths or lines dividing extensions 18, such as joint 28 shown inFIGS. 1 and 2. In another embodiment, represented in FIG. 7, lines orpaths 29 are included between extensions 18. Paths 29 provide controlledtear of the dressing support layer 16 when tabs 23 are lifted to removethe dressing support layer 16 during and/or after application of thedressing 10 to a patient. However, alternative configurations arepossible including but not limited to linear, angled, Y-shaped,dual-angled offset, circular holes, and alternating combinationsthereof. In FIG. 7, path 29 is shown with a plurality of perforations inan arrow configuration.

The wound dressing 10 is typically applied to a patient by firstcleaning the wound and making sure the area around the wound is ready toreceive a dressing. The carrier film 24 is then removed from thedressing, exposing the bottom of the absorbent pad 12 and the perimeterof the adhesive layer 17 and the backing layer 14. This perimeter of thebacking layer 14 is maintained in a generally planer or stretchedorientation by the numerous extensions 18 in the support layer 16. Thecenter of the absorbent pad 12 is brought in contact with the wound, andthen the edges of the dressing 10 are gently and smoothly pressedagainst the patient, thereby bringing the exposed adhesive perimeter ofthe backing layer 14 in contact with the patient. Generally the areas 20of the backing layer 14 intermediate the extensions 18 contract toconform around the skin surface. When applied to convex surfaces, thecontractions can cause the tabs 23 to rise off the surface of thebacking layer 14. After the dressing 10 is properly in position andadhered to a patient's skin, the support layer 16 can be removed.Generally removal of support layer 16 is accomplished by grasping tabs23 and then using a peeling motion toward the edges of the dressing 10to remove the support layer 16.

Pressure sensitive adhesive layer 17 is generally provided on one majorsurface of the backing layer 14 in order to make it adhesive, and a lowadhesion coating (low adhesion backsize or LAB) is provided on the othermajor surface of the backing layer 14 on the side that comes in contactwith the support layer 16. The low adhesion coating reduces the need tochange the dressing 10 due to unwanted dressing removal when other tapesor devices are placed on the dressing 10 and removed, and reduces thesurface friction of the dressing 10 on linen or other fabrics, therebyoffering additional protection against the accidental removal ofdressing 10. A description of a low adhesion backing material suitablefor use with the present invention can be found in U.S. Pat. Nos.5,531,855 and 6,264,976, which are compatible with a heat seal bonddescribed below, and are incorporated herein in their entirety.

When the support layer 16 is removed from the backing layer 14, theforce applied to the edge of the backing layer 14 is generallyperpendicular to the perimeter of the dressing 10. This force contrastswith peel forces of conventional support layers, which are parallel tothe perimeter of the wound dressing, and which often lift the perimeteroff the surface of the patient, potentially loosening the dressing orcreating a path for leakage of fluids from the wound.

The absorbent pad 12 of dressing 10 is sometimes referred to as an“island pad” because the backing layer 14 extends substantially beyondthe absorbent pad 12, typically beyond the entire periphery of theabsorbent pad 12. For example, the length and width of the absorbent padcan be 6 cm by 6 cm, while a backing for this pad can be 9 cm by 9 cm.The pressure sensitive adhesive layer 17 on the peripheral portion ofthe backing layer 14 is thus not supported or reinforced by therelatively heavy and stiff absorbent pad 12, and absent the benefits ofdressing support layer 16 would be difficult to handle without folding,wrinkling or otherwise adhering to itself, rather than adhering to theskin, before and during application.

The support layer 16 is preferably attached to the second major surfaceof the backing layer 14 (over the low adhesion backing). The bondbetween the support layer 16 and the backing layer 14 is stronger thanthe bond between the pressure sensitive adhesive 17 and the carrierlayer 24 so that the backing layer 14 remains attached to the supportlayer 16 when the carrier layer 24 is removed from the dressing 10. Oncethe carrier layer 24 and dressing 10 are separated, only the supportlayer 16 and absorbent pad 12 provide significant rigidity to thebacking layer 14.

The absorbent pad 12 can comprise a hydrocolloid and hydrogel pad havinga thickness of at least 1 mm (e.g., most preferably 3-9 mm), and thebacking layer 14 can comprise a transparent elastic polymeric film(e.g., urethane) having a thickness no greater than 0.1 mm (e.g., mostpreferably 0.021-0.051 mm). It will be appreciated that in thisembodiment the absorbent pad 12 is much thicker, stiffer and heavierthan the backing layer 14.

In reference now to FIGS. 5, 6, and 7, alternative wound dressingimplementations are shown. In FIGS. 5 and 6, different shapes for thewound dressings are shown. The embodiment shown in FIG. 5 is an ovalshaped wound dressing 50 with an absorbent pad 52, adhesive backing 54,and support 56. The embodiment shown in FIG. 6 is a square shaped wounddressing 60 with an absorbent pad 62, adhesive backing 64, and support66. In FIG. 7, the various portions of the support layer are shownconnected by a tear path of perforations.

Additional aspects of various components of the invention will now bedescribed in greater detail.

Absorbent Pad

Absorbent pad 12 can be manufactured of any of a variety of materialsincluding, but not limited to, woven or nonwoven cotton or rayon.Absorbent pad 12 is useful for containing a number of substances,optionally including antimicrobial agents, drugs for transdermal drugdelivery, chemical indicators to monitor hormones or other substances ina patient, etc.

The absorbent may include a hydrocolloid composition, including thehydrocolloid compositions described in U.S. Pat. Nos. 5,622,711 and5,633,010, the disclosures of which are hereby incorporated byreference. The hydrocolloid absorbent may comprise, for example, anatural hydrocolloid, such as pectin, gelatin, or carboxymethylcellulose(CMC) (Aqualon Corp., Wilmington, Del.), a semi-synthetic hydrocolloid,such as cross-linked carboxymethylcellulose (X4ink CMC) (e.g. Ac-Di-Sol;FMC Corp., Philadelphia, Pa.), a synthetic hydrocolloid, such ascross-linked polyacrylic acid (PAA) (e.g., CARBOPOL™ No. 974P; B.F.Goodrich, Brecksville, Ohio), or a combination thereof. Generally, thehydrocolloid absorbent component comprises from about 5 percent to about60 percent by weight of the absorbent composition. When preparing anabsorbent composition for use in a wound dressing the hydrocolloidabsorbent preferably comprises from about 20 percent to about 40 percentby weight of the composition. Absorbent materials may also chosen fromother synthetic and natural hydrophilic materials including polymer gelsand foams.

Backing Materials

Suitable backing materials for backing layer 14 include, for example,nonwoven fibrous webs, woven fibrous webs, knits, films and otherfamiliar backing materials. The backing materials are typicallytranslucent or transparent polymeric elastic films. The backing can be ahigh moisture vapor permeable film backing. U.S. Pat. No. 3,645,835, thedisclosure of which is hereby incorporated by reference, describesmethods of making such films and methods for testing their permeability.

The backing advantageously should transmit moisture vapor at a rateequal to or greater than human skin. In some embodiments, the adhesivecoated backing layer transmits moisture vapor at a rate of at least 300g/m²/24 hrs/37° C./100-10% RH, frequently at least 700 g/m²/24 hrs/37°C./100-10% RH, and most typically at least 2000 g/m²/24 hrs/37°C./100-10% RH using the inverted cup method.

The backing layer 14 is generally conformable to anatomical surfaces. Assuch, when the backing layer 14 is applied to an anatomical surface, itconforms to the surface even when the surface is moved. The backinglayer 14 is also conformable to animal anatomical joints. When the jointis flexed and then returned to its unflexed position, the backing layer14 can be made such that it stretches to accommodate the flexion of thejoint, but is resilient enough to continue to conform to the joint whenthe joint is returned to its unflexed condition.

A description of this characteristic of backing layers 14 for use withthe present invention can be found in issued U.S. Pat. Nos. 5,088,483and 5,160,315, the disclosures of which are hereby incorporated byreference in their entirety. Specific suitable backing materials areelastomeric polyurethane, co-polyester, or polyether block amide films.These films combine the desirable properties of resiliency, highmoisture vapor permeability, and transparency found in backings.

Support Layer

The material used to form the support layer 16 is generallysubstantially more rigid than the backing layer 14 to prevent thebacking layer 14 from improperly wrinkling during application to apatient. The support layer 16 can be heat-sealable to the backing layer14 with or without a low adhesion coating described above. In general,the support layer materials can include, but are not limited to,polyethylene/vinyl acetate copolymer-coated papers and polyester films.One example of a suitable support layer material is a polyethylene/vinylacetate copolymer coated super calendared Kraft paper (1-80BKG-157 PE;DCP-Lohya of Dixon, Ill.).

The support layer 16 can include perforations to aid in separatingportions of the support layer 16 after application of the dressing 10 ina patient. Spacing and shape of the perforations are adjusted to give asupport layer with relatively easy to tear performance on removal of thesupport layer from the applied dressing. The perforations may be shapedin accordance with any of the accepted perforation patterns includinglinear, angled, Y-shaped, V-shaped, dual-angled offset, sinusoidal, etc.

Pressure Sensitive Adhesive

Various pressure sensitive adhesives can be used to form adhesive layer17 on the backing layer 14 to make it adhesive. The pressure sensitiveadhesive is usually reasonably skin compatible and “hypoallergenic”,such as the acrylate copolymers described in U.S. Pat. No. RE 24,906,the disclosure of which is hereby incorporated by reference.Particularly useful is a 97:3 iso-octyl acrylate: acrylamide copolymer,as is 70:15:15 isooctyl acrylate: ethyleneoxide acrylate: acrylic acidterpolymer described in U.S. Pat. No. 4,737,410, the disclosure of whichis hereby incorporated by reference is suitable. Additional usefuladhesives are described in U.S. Pat. Nos. 3,389,827, 4,112,213,4,310,509, and 4,323,557, the disclosures of which are herebyincorporated by reference. Inclusion of medicaments or antimicrobialagents in the adhesive is also contemplated, as described in U.S. Pat.Nos. 4,310,509 and 4,323,557, both of which are also hereby incorporatedby reference.

Carrier Films

Carrier films 24 suitable for use with the invention can be made ofkraft papers, polyethylene, polypropylene, polyester or composites ofany of these materials. The films are preferably coated with releaseagents such as fluorochemicals or silicones. For example, U.S. Pat. No.4,472,480, the disclosure of which is hereby incorporated by reference,describes low surface energy perfluorochemical liners. The liners arepapers, polyolefin films, or polyester films coated with siliconerelease materials. Examples of commercially available silicone coatedrelease papers are POLYSLIK™, silicone release papers available fromRexam Release (Bedford Park, Ill.) and silicone release papers suppliedby DCP-Lohya Co. (Dixon, Ill.).

As various changes could be made in the above constructions,compositions and methods without departing from the scope of theinvention as defined in the claims, it is intended that all mattercontained in the above description or shown in the accompanying drawingsbe interpreted as illustrative and not in a limiting sense.

1. A wound dressing support system, comprising: a wound dressingcomprising a backing layer; and a wound dressing support layer; and aplurality of centrally located tabs configured for removing the supportlayer from the backing layer; wherein the perimeter of the support layeris releasably adhered to the backing layer, but at least one of thecentrally located tabs is not adhered to the backing layer; wherein theforce applied to the edge of the backing layer is generallyperpendicular to the perimeter of the dressing when the support layer isremoved from the backing layer.
 2. The wound dressing support system ofclaim 1, wherein less than 80 percent of the backing layer is covered bythe support layer.
 3. The wound dressing support system of claim 1,wherein less than 60 percent of the backing layer is covered by thesupport layer.